Esters of 5-aminolevulinic acid as photosensitizing agents in photochemotherapy

ABSTRACT

The present invention relates to compounds being esters of 5-aminolevulinic acids or pharmaceutically acceptable salts thereof, including compounds of formula (I) R22N—CH2COCH2-CH2CO—OR1 (wherein R1 may represent alkyl optionally substituted by hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, amino, aryl, oxo or fluoro groups and optionally interrupted by oxygen, nitrogen, sulphur or phosphorus atoms; and R2 represents a hydrogen atom or a group R1, and both R2 groups may be the identical or different), and their use in diagnosis and photochemotherapy of disorders or abnormalities of external or internal surfaces of the body, and products and kits for performing the invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior U.S. patent application Ser. No. 10/818,917 filed Apr. 5, 2004, now U.S. Pat. No. 7,530,467, which was a continuation-in-part of U.S. patent application Ser. No. 10/165,667 filed Jun. 7, 2002, now abandoned which is a continuation of U.S. patent application Ser. No. 09/471,620, filed Dec. 21, 1999, now U.S. Pat. No. 6,492,420 which is a continuation of U.S. patent application Ser. No. 08/913,257, filed on Dec. 5, 1997 now U.S. Pat. No. 6,034,267, which is a National Phase Application of PCT International Application No. PCT/GB96/00553 filed on Mar. 8, 1996.

The present invention relates to derivatives of 5-aminolevulinic acid (ALA) and in particular to esters of ALA for use as photosensitizing agents in photochemotherapy or diagnosis.

Photochemotherapy, or photodynamic therapy (PDT) as it is also known, is a recently up-coming technique for the treatment of various abnormalities or disorders of the skin or other epithelial organs or mucosa, especially cancers or pre-cancerous lesions, as well as certain non-malignant lesions for example skin complaints such as psoriasis. Photochemotherapy involves the application of photosensitizing (photochemotherapeutic) agents to the affected area of the body, followed by exposure to photoactivating light in order to activate the photosensitizing agents and convert them into cytotoxic form, whereby the affected cells are killed or their proliferative potential diminished.

A range of photosensitizing agents are known, including notably the psoralens, the porphyrins, the chlorins and the phthalocyanins. Such drugs become toxic when exposed to light.

Photosensitizing drugs may exert their effects by a variety of mechanisms, directly or indirectly. Thus for example, certain photosensitizers become directly toxic when activated by light, whereas others act to generate toxic species, e.g. oxidizing agents such as singlet oxygen or other oxygen-derived free radicals, which are extremely destructive to cellular material and biomolecules such as lipids, proteins and nucleic acids. Psoralens are an example of directly acting photosensitizers; upon exposure to light they form adducts and cross-links between the two strands of DNA molecules, thereby inhibiting DNA synthesis. The unfortunate risk with this therapy is that unwanted mutagenic and carcinogenic side effects may occur.

This disadvantage may be avoided by selecting photosensitizers with an alternative, indirect mode of action. For example porphyrins, which act indirectly by generation of toxic oxygen species, have no mutagenic side-effects and represent more favorable candidates for photochemotherapy. Porphyrins are naturally occurring precursors in the synthesis of heme. In particular, heme is produced when iron (Fe³⁺) is incorporated in protoporphyrin IX (Pp) by the action of the enzyme ferrochelatase. Pp is an extremely potent photosensitizer, whereas heme has no photosensitizing effect.

One such porphyrin-based drug, Photofrin, has recently been approved as a photosensitizer in the therapy of certain cancers. The main disadvantage is that since it must be administered parenterally, generally intravenously, cause photosensitization of the skin which may last for several weeks following i.v. injection. Photofrin consists of large oligomers of porphyrin and it does not readily penetrate the skin when applied topically. Similar problems exist with other porphyrin-based photosensitizers such as the so-called “hematoporphyrin derivative” (Hpd), which has also been reported for use in cancer photochemotherapy (see for example S. Dougherty. J. Natl. Cancer Ins., 1974, 52; 1333; Kelly and Snell, J. Uro., 1976, 115:150). Hpd is a complex mixture obtained by treating hematoporphyrin with acetic and sulphuric acids, after which the acetylated product is dissolved with alkali.

To overcome these problems, precursors of Pp have been investigated for photochemotherapeutic potential. In particular the Pp precursor 5-aminolevulinic acid (ALA) has been investigated as a photochemotherapeutic agent for certain skin cancers. ALA, which is formed from succinyl CoA and glycine in the first step of heme synthesis, is to a limited extent able to penetrate the skin and lead to a localized build-up of Pp; since the action of ferrochelatase (the metallating enzyme) is the rate limiting step in heme synthesis, an excess of ALA leads to accumulation of Pp, the photosensitizing agent. Thus, by applying ALA topically to skin tumours, and then after several hours exposing the tumours to light, a beneficial photochemotherapeutic effect may be obtained (see for example WO91/01727). Since the skin covering basilomas and squamous cell carcinomas is more readily penetrated by ALA than healthy skin, and since the concentration of ferrochelatase is low in skin tumours, it has been found that topical application of ALA leads to a selectively enhanced production of Pp in tumours.

However, whilst the use of ALA represents a significant advance in the art, photochemotherapy with ALA is not always entirely satisfactory. ALA is not able to penetrate all tumours and other tissues with sufficient efficacy to enable treatment of a wide range of tumours or other conditions and ALA also tends to be unstable in pharmaceutical formulations. A need therefore exists for improved photochemotherapeutic agents.

The present invention addresses this need and in particular aims to provide photochemotherapeutic agents which are better able to penetrate the tumour or other abnormality, and which have an enhanced photochemotherapeutic effect over those described in the prior art.

In one aspect, the present invention thus provides compounds being esters of 5-aminolevulinic acids or pharmaceutically acceptable salts thereof, for use in photochemotherapy or diagnosis of bladder cancer and cervical cancer.

In the esters for use according to the invention the 5-amino group may be substituted or unsubstituted, the latter case being the ALA esters.

More particularly, the compounds for use according to the invention are esters of 5-aminolevulinic acids with optionally substituted alkanols, i.e. alkyl esters or substituted alkyl esters.

Database Xfire entries 3060978, 5347132, 5499790, 5620924, 5633390, 5991317 and 6517740 (Beilstein); Cosmo Sogo Kenkyusho K K, Patent Abstracts of Japan Vol. 16; No. 156 (C-0930), 16.41992; EP-A-316179 (Tokuyama Soda KK); GB-A-2058077 (Hudson et al.); and DE-A-2411382 (Boehringer Sohn Ingelheim) describe alkyl ester derivative 5-aminolevulinic acid, and derivatives and salts thereof and processes for their preparation.

Alternatively viewed, the invention can therefore be seen to employ compounds of formula I, R₂ ²N—CH₂COCH₂—CH₂CO—OR¹  (I) (wherein R¹ may represent alkyl optionally substituted by hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, amino, aryl, oxo or fluoro groups and optionally interrupted by oxygen, nitrogen, sulphur or phosphorus atoms; and R² each of which may be the same or different, represents a hydrogen atom or a group R¹) and salts thereof for use in photochemotherapy or diagnosis.

The substituted alkyl R¹ groups may be mono or poly-substituted. Thus suitable R¹ groups include for example unsubstituted alkyl, alkoxyalkyl, hydroxyalkoxyalkyl, polyhydroxyalkyl, hydroxy poly alkyleneoxyalkyl and the like. The term “acyl” as used herein includes both carboxylate and carbonate groups, thus, acyloxy substituted alkyl groups include for example alkylcarbonyloxy alkyl. In such groups any alkylene moieties preferably have carbon atom contents defined for alkyl groups below. Preferred aryl groups include phenyl and monocyclic 5-7 membered heteroaromatics, especially phenyl and such groups may themselves optionally be substituted.

Representative substituted alkyl groups R¹ include alkoxymethyl, alkoxyethyl and alkoxypropyl groups or acyloxymethyl, acyloxyethyl and acyloxypropyl groups e.g. pivaloyloxymethyl.

Preferred compounds for use according to the invention, include those wherein R¹ represents an unsubstituted alkyl group and/or each R² represents a hydrogen atom.

As used herein, the term “alkyl” includes any long or short chain, straight-chained or branched aliphatic saturated or unsaturated hydrocarbon group. The unsaturated alkyl groups may be mono- or polyunsaturated and include both alkenyl and alkynyl groups. Such groups may contain up to 40 carbon atoms. However, alkyl groups containing up to 10 e.g. 8, more preferably up to 6, and especially preferably up to 4 carbon atoms are preferred.

Particular mention may be made of ALA-methylester, ALA-ethylester, ALA-propylester, ALA-hexylester, ALA-heptylester and ALA-octylester and salts thereof, which represent preferred compounds for use according to the invention.

The Tumor Registry of Geneva among others shows that in the last decade there has been a decrease in the incidence of invasive cancer of the cervix. However, the data show an increasing incidence of intraepithelial lesions in younger women. Standard treatment for these patients is excisional methods (cold knife conization or loop electrosurgical procedure) or ablative methods (cryotherapy or laser vaporization). The side effects and consequences of these procedures include bleeding, infections, cervical stenosis, infertility and preterm delivery (Leiman et al. (1980), Am. J. Obstet. Gynecol. 136: 14-18; Hagen et al. (1993), Br. J. Obstet. and Gynecol. 100: 717-720; Hagen et al. (1998), Acta Obstet. Gynecol. Scand. 77: 558-563). Treatment is often repeated. The recurrence rate is 2.9% with free margins after conization and 22% with involved margins (Phelps et al. (1994), Obstet. Gynecol. 84: 128). With new procedures like LEEP (electrosurgical excision procedure) the recurrence rate is even higher and ranges between 5% and 69% (Gonzales et al. (2001), Am. J. Obstet. Gynecol. 184: 315). There is therefore a need of a tissue sparing procedure to minimize the risk of these complications.

Thus, in a further aspect, the invention comprises a specific treatment of intraepithelial lesions that spares stromal tissue. In one embodiment, this comprises application of hexyl aminolevulinate to the cervix and subsequent fluorescent detection of cervical intraepithelial lesions. Such lesions can subsequently be destroyed by application of light of the appropriate wavelength.

Bladder cancer is the fourth most common malignant neoplasm in men and the eighth most common in women (NIH Publication no. 90-722 (1990) & NIH Publication no. 94-2789 (1994)) with approximately 200,000 new cases diagnosed every year. The highest incidence of bladder cancer is found in industrialized countries such as the United States (US), Canada, Denmark, Italy and Spain (NIH Pub No. 96-4104 (1996), and the incidence rises with age. The lifetime chance of developing bladder cancer is over 3% (NIH Publication no. 94-2789 (1994)).

Survival is strongly associated with early detection. The major prognostic factors are the depth of penetration into the bladder wall and the degree of differentiation of the tumor. In the 20 years following diagnosis globally there is a recurrence rate of 50 to 75%, and a mortality rate of 10 to 30% (Abel (1993), Brit. J. Urol. 72(2): 135-142; Herr (1997), World J. Urol. 15(2): 84-88; Holmang et al. (1995), J. Urol. 53(6): 1823-1827).

In patients with the diagnosis of bladder cancer, 70-80% present with superficial tumors. Diagnosis is commonly confirmed by urinalysis, urine cytology, flow cytometry and cystoscopic examination including biopsy. Some of these methods are relatively insensitive and may not detect all tumors, particularly small low-grade tumors (dysplasia and superficial tumors) which are easily overlooked. These lesions are predictive of recurrence and progression of disease, and the identification of these lesions is a crucial factor for the prognosis of the patient (W of & Højgard (1983), Lancet 16: 134-136). The present situation with 50-75% recurrence rate shows the inadequacy of white light cystoscopy for detection and resection of the lesions. Bacillus Calmette-Guerin treatment is an efficient treatment for superficial tumors and has been shown to reduce recurrence and progression of disease (Smith et al. (1999), J. Neurol. 162: 1697-1701). The benefits of chemotherapy are questioned but may delay recurrence (Pawinski et al. (1995), J. Urol. 153: 1934-1941). Treatment of invasive disease includes cystectomy and systemic chemotherapy which is associated with high morbidity for the patients. A better detection of papillary bladder cancer and early detection of CIS lesions will provide the patient with a more optimal pharmacological treatment when needed, may reduce the need for follow-up cystoscopies and hopefully result in a better prognosis for the patient.

The compounds for use in the invention may be prepared using standard processes and procedures well-known in the art for derivatization of multi-functional compounds, and especially esterification. As known in the art, such esterification of compounds may involve protection and deprotection of appropriate groups such that only the required groups remain active and take part in the reaction under the conditions of the esterification. Thus for example the substituents of substituted alkanols used to prepare the esters may be protected during esterification. Similarly the NR₂ ² group on the compound contributing this group to compounds of formula I may be protected during the reaction and deprotected thereafter. Such protection/deprotection procedures are well known in the art for the preparation of derivatives, and in particular, esters of well known amino-acids, see for example Mcomie in “Protective Groups in Organic Chemistry”, Plenum, 1973 and T. W. Greene in “Protective Groups in Organic Chemistry”, Wiley-Interscience, 1981.

In a further aspect, the present invention thus provides a process for preparing the compounds for use in the invention, comprising forming an ester of the carboxy group of a 5-aminolevulinic acid.

The invention can thus be seen to provide a process for preparing the compounds for use in the invention, comprising reacting a 5-aminolevulinic acid, or an esterifiable derivative thereof, with an alkanol or an ester-forming derivative thereof.

More particularly, this aspect of the invention provides a process for preparing compounds of formula I, which process comprises at least one of the following steps:

(a) reacting a compound of formula II R₂ ²N—CH₂COCH₂—CH₂CO—X  (II) (wherein X represents a leaving group, for example a hydroxyl group, a halogen atom or alkoxy group or COX represents an acid anhydride group and R² is as hereinbefore defined)

with a compound of formula III R¹—OH  (III) (wherein R¹ is as hereinbefore defined); and (b) converting a compound of formula I into a pharmaceutically acceptable salt thereof.

The reaction of step (a) may conveniently be carried out in a solvent or mixture of solvents such as water, acetone, diethylether, methylformamide, tetrahydrofuran etc. at temperatures up to the boiling point of the mixture, preferably at ambient temperatures.

The conditions of the esterification reactions will depend on the alcohol used and the conditions may be chosen such that maximum yield of the ester is obtained. Since the esterification reactions are reversible equilibrium reactions, reaction conditions may be selected in such a way that maximum yield of the ester product is obtained. Such conditions may be obtained by selecting a solvent which is capable of removing the water formed in a typical esterification reaction by forming an azeotrope with water. Such solvents are exemplified by aromatic hydrocarbons or others capable of forming azeotropes with water, e.g. some chlorinated hydrocarbons such as chloroform. For the formation of the lower esters of 5-ALA the equilibrium reaction may be driven to the ester side by using a large excess of the alcohol. With other esters the equilibrium may be driven towards the ester product by using a large excess of the acid.

Esterification reactions are well-known in the art for example, as described by Saul Patai in “The chemistry of the carboxylic acids and esters”, (Ch. 11, p. 505, Interscience 1969) and Houban Weyl, (Methoden der Organische Chemie, Band ES, “Carbonsauren und carbonsauren-derivate”, p. 504, Georg Thieme Verlag, 1985). The formation of derivatives of amino-acids are described in Band XI/2 of the same series, (Houben Weyl, Methoden der Organische Chemie, Band XI/2, “Stickstoffverbindungen”, p. 269, Georg Thieme Verlag, 1958).

The reaction will conveniently be carried out in the presence of a catalyst, eg. an inorganic or organic acid or an acid binding agent such as a base.

The compounds used as starting materials are known from the literature, and in many cases commercially available, or may be obtained using methods known per se. ALA, for example, is available from Sigma or from Photocure, Oslo, Norway.

As mentioned above, the compounds for use according to the invention may take the form of pharmaceutically acceptable salts. Such salts preferably are acid addition salts with physiologically acceptable organic or inorganic acids. Suitable acids include, for example, hydrochloric, hydrobromic, sulphuric, phosphoric, acetic, lactic, citric, tartaric, succinic, maleic, fumaric and ascorbic acids. Procedures for salt formation are conventional in the art.

As mentioned above, the compounds for use in the invention and their salts have valuable pharmacological properties, namely a photosensitizing agent which renders them useful as photochemotherapeutic agents.

Like ALA, the compounds exert their effects by enhancing production of Pp; upon delivery to the desired site of action hydrolytic enzymes such as esterases present in the target cells break down the esters into the parent ALA, which then enters the haem synthesis pathway and leads to a build-up of Pp. However, the compounds for use in the invention have a number of advantages over ALA itself. Firstly, the compounds are better able to penetrate skin and other tissues as compared with ALA; the penetration is both deeper and faster. This is an important advantage, especially for topical administration. Secondly, the esters have surprisingly been found to be better enhancers of Pp production than ALA; Pp production levels following administration of the ALA esters are higher than with ALA alone. Thirdly, the compounds for use in the invention demonstrate improved selectivity for the target tissue to be treated, namely the Pp production-enhancing effect is localised to the desired target lesion and does not spread to the surrounding tissues. This is especially evident with tumours. Finally, the compounds appear to localise better to the target tissue upon administration. This is especially important for systemic application, since it means that undesirable photosensitization effects, as reported in the literature for other porphyrin-based photosensitizers, may be reduced or avoided.

A further aspect of the present invention accordingly provides a pharmaceutical composition comprising a compound as described hereinbefore, or a pharmaceutically acceptable salt thereof, together with at least one pharmaceutical carrier or excipient.

In a still further aspect, there is also provided the use of a compound as described hereinbefore, or a pharmaceutically acceptable salt thereof, for the preparation of a therapeutic agent for use in photochemotherapy, and especially for the treatment of disorders or abnormalities of external or internal surfaces of the body which are responsive to photochemotherapy.

As disclosed in U.S. Pat. No. 6,034,267, the abnormalities and disorders which may be treated with esters of 5-aminolevulinic acid include any malignant, pre-malignant and non-malignant abnormalities or disorders responsive to photochemotherapy eg. tumours or other growths, skin disorders such as psoriasis or actinic keratoses, skin abrasions, and other diseases or infections eg. bacterial, viral or fungal infections, for example Herpes virus infections. The invention is particularly suited to the treatment of diseases, disorders or abnormalities where discrete lesions are formed to which the compositions may be directly applied (lesions is used here in a broad sense to include tumours and the like).

It has been found that certain esters of 5-aminolevulinic acid are particularly useful in detecting and treating Barrets oesophagus; colorectal cancer; lesions in mouth, pharynx and larynx; lesions or cancers of the vulva, cervix, ovary; brain tumors; mammary tumors; bladder cancer, for example carcinoma in situ. As described in further detail herein, hexyl aminolevulinate is suitable, for example, for detecting and treating urological lesions such as bladder cancer, for example carcinoma in situ, papillary lesions and invasive carcinoma, premalignant lesions such as hyperplasias and dysplasias, and cervical lesions such as cervical intraepithelial neoplasia, carcinoma in situ, and invasive carcinoma, and premalignant lesions such as atypical squamous cells of undetermined significance (ASCUS) or atypical glandular cells of undetermined significance (AGCUS).

The internal and external body surfaces which may be treated with esters of 5-aminolevulinic acid as described in U.S. Pat. No. 6,034,267 include the skin and all other epithelial and serosal surfaces, including for example mucosa, the linings of organs e.g. the respiratory, gastro-intestinal and genito-urinary tracts, and glands with ducts which empty onto such surfaces (e.g. liver, hair follicles with sebaceous glands, mammary glands, salivary glands and seminal vesicles). In addition to the skin, such surfaces include for example the lining of the vagina, the endometrium and the urothelium. Such surfaces may also include cavities formed in the body following excision of diseased or cancerous tissue eg. brain cavities following the excision of tumours such as gliomas.

Exemplary surfaces thus include: (i) skin and conjunctiva; (ii) the lining of the mouth, pharynx, oesophagus, stomach, intestines and intestinal appendages, rectum, and anal canal; (iii) the lining of the nasal passages, nasal sinuses, nasopharynx, trachea, bronchi, and bronchioles; (iv) the lining of the ureters, urinary bladder, and urethra; (v) the lining of the vagina, uterine cervix, and uterus; (vi) the parietal and visceral pleura; (vii) the lining of the peritoneal and pelvic cavities, and the surface of the organs contained within those cavities; (viii) the dura mater and meninges; (ix) any tumors in solid tissues that can be made accessible to photoactivating light e.g. either directly, at time of surgery, or via an optical fibre inserted through a needle.

As disclosed in U.S. Pat. No. 6,034,267, the compositions containing esters of 5-aminolevulinic acid may be formulated in conventional manner with one or more physiologically acceptable carriers or excipients, according to techniques well known in the art. Compositions may be administered topically, orally or systemically. Topical compositions are preferred, and include gels, creams, ointments, sprays, lotions, salves, sticks, soaps, powders, pessaries, aerosols, drops and any of the other conventional pharmaceutical forms in the art.

Ointments and creams may, for example, be formulated with an aqueous or oily base with the addition of suitable thickening and/or gelling agents. Lotions may be formulated with an aqueous or oily base and will, in general, also contain one or more emulsifying, dispersing, suspending, thickening or colouring agents. Powders may be formed with the aid of any suitable powder base. Drops may be formulated with an aqueous or non-aqueous base also comprising one or more dispersing, solubilising or suspending agents. Aerosol sprays are conveniently delivered from pressurised packs, with the use of a suitable propellant.

Alternatively, the compositions may be provided in a form adapted for oral or parenteral administration, for example by intradermal, subcutaneous, intraperitoneal or intravenous injection. Alternative pharmaceutical forms thus include plain or coated tablets, capsules, suspensions and solutions containing the active component optionally together with one or more inert conventional carriers and/or diluents, e.g. with corn starch, lactose, sucrose, microcrystalline cellulose, magnesium stearate, polyvinylpyrrolidone, citric acid, tartaric acid, water, water/ethanol, water/glycerol, water/sorbitol, water/polyethyleneglycol, propyleneglycol, stearylalcohol, carboxymethylcellulose or fatty substances such as hard fat or suitable mixtures thereof. A cream or gel containing an ester of 5-aminolevulinic acid for use in treating or detecting cervical abnormalities could be packaged, for example, in a tube such as a collapsible tube, in a prefilled syringe, or in a vaginal capsule.

For the treatment and detection of bladder cancer, the dosage form is preferably an isotonic solution containing hexyl 5-aminolevulinate (HAL), for example phosphate buffered saline (PBS), optionally containing carriers or excipients such as local anesthetic (e.g. lidocaine) and chelating agents (e.g. EDTA or desferroxamine). An example of such a solution is 4.3 mM KH2PO4, 4.3 mM Na2HPO4, 120 mM NaCl, pH 6.0 containing 4-16 mM HAL for diagnosis, preferably 8 mM HAL, or 1-20 mM HAL for therapy, preferably 8 mM HAL. For the treatment and detection of cervical cancer, the dosage form is preferably a cream, gel or hydrogel containing 1-20 mM HAL or 0.025-0.5% (w/v) HAL hydrochloride salt. For detection, a HAL concentration of 10 mM is preferred, while for treatment, a concentration of 20 mM is preferred. An exemplary cream could further comprise 21% (v/v) cetyl alcohol as an emollient, 19% (v/v) liquid paraffin as an emollient, 0.5% (v/v) monoleylsorbitane (SPAN 80) as an emulsifying agent or surfactant, 4.5% (v/v) monoleylpolysorbitane (Tween 80) as an emulsifying agent or surfactant, 0.1% (v.v) chlorhexidine digluconate as an antimicrobial, and distilled water q.s. 100%.

The concentration of the compounds as described hereinbefore in the compositions, depends upon the nature of the compound, the composition, mode of administration and the patient and may be varied or adjusted according to choice. Generally however, concentration ranges of 1 to 50% (w/w) are suitable. For therapeutic applications concentration ranges of 10 to 50% have been found to be suitable, eg. 15 to 30% (w/w).

Following administration to the surface, the area treated is exposed to light to achieve the photo-chemotherapeutic effect. The length of time following administration, at which the light exposure takes place will depend on the nature of the composition and the form of administration. This can generally be in the order of 0.5 to 48 hours, e.g. 1 to 10 hours.

The irradiation will in general be applied at a dose level of 40 to 200 Joules/cm², for example at 100 Joules/cm². Illumination time depends on the output in mW/cm², as discussed below.

For the detection of bladder cancer, HAL is administered to tissue or tissue sample for a period of time which can range, for example, from 0.5 to 4 hours. The tissue or tissue sample subsequently is exposed to photoactivating light, for example 0 to 2 hours following HAL administration. The light dosage can be about 0.2 to 0.4 J/cm². For example, using a light source providing 80 mW blue light of wavelength in the range of about 375-440 nm and a human bladder with internal surface area of 300 cm² (0.27 mW/cm²), light is administered for 12 to 24 minutes. These specifications vary in accordance with the wavelength of light used.

For the treatment of bladder cancer, HAL is administered to tissue or tissue sample for a period of time which can range, for example, from 0.5 to 4 hours. The tissue or tissue sample subsequently is exposed to photoactivating light, for example 0 to 2 hours following HAL administration. The light dosage can be about 15 to 100 J/cm². For example, using a light source providing 100 mW/cm², light is administered for about 2.5 to 17 minutes. These specifications vary in accordance with the wavelength of light used (for example, red light instead of white light).

For the detection of cervical intraepithelial lesions, HAL is administered to tissue or tissue sample for about 1 to 3 hours. The tissue or tissue sample is then exposed to photoactivating light about 0 to 2 hours following HAL administration. Light dosage is the same as for detection of bladder lesions, discussed above.

For the treatment of cervical intraepithelial lesions, HAL is administered to tissue or tissue sample for about 1-12 hours. The tissue or tissue sample is then exposed to photoactivating light about 0 to 2 hours following HAL administration. Light dosage is 10-100 J/cm² of red light. For example, light providing 100 mW/cm² of red light.

The wavelength of light used for irradiation may be selected to achieve a more efficaceous photochemo-therapeutic effect. Conventionally, when porphyrins are used in photochemotherapy they are irradiated with light at about the absorption maximum of the porphyrin. Thus, for example in the case of the prior art use of ALA in photochemotherapy of skin cancer, wavelengths in the region 350-640 nm, preferably 610-635 nm were employed. However, by selecting a broad range of wavelengths for irradiation, extending beyond the absorption maximum of the porphyrin, the photosensitizing effect may be enhanced. Whilst not wishing to be bound by theory, this is thought to be due to the fact that when Pp, and other porphyrins, are exposed to light having wavelengths within its absorption spectrum, it is degraded into various photo-products including in particular photoprotoporphyrin (PPp). PPp is a chlorin and has a considerable photo-sensitizing effect; its absorption spectrum stretches out to longer wavelengths beyond the wavelengths at which Pp absorbs ie. up to almost 700 nm (Pp absorbs almost no light above 650 nm). Thus in conventional photochemotherapy, the wavelengths used do not excite PPp and hence do not obtain the benefit of its additional photosensitizing effect. Irradiation with wavelengths of light in the range 500-700 nm has been found to be particularly effective. It is particularly important to include the wavelengths 630 and 690 nm.

A further aspect of the invention thus provides a method of photochemotherapeutic treatment of disorders or abnormalities of external or internal surfaces of the body, comprising administering to the affected surfaces, a composition as hereinbefore defined, and exposing said surfaces to light, preferably to light in the wavelength region 300-800 nm, for example 500-700 nm.

Methods for irradiation of different areas of the body, eg. by lamps or lasers are well known in the art (see for example Van den Bergh, Chemistry in Britain, May 1986 p. 430-439).

The compounds for use in the invention may be formulated and/or administered with other photosensitizing agents, for example ALA or photofrin, or with other active components which may enhance the photochemotherapeutic effect. For example, chelating agents may beneficially be included in order to enhance accumulation of Pp; the chelation of iron by the chelating agents prevents its incorporation into Pp to form haem by the action of the enzyme ferrochelatase, thereby leading to a build-up of Pp. The photosensitizing effect is thus enhanced.

Aminopolycarboxylic acid chelating agents are particularly suitable for use in this regard, including any of the chelants described in the literature for metal detoxification or for the chelation of paramagnetic metal ions in magnetic resonance imaging contrast agents. Particular mention may be made of EDTA, CDTA (cyclohexane diamine tetraacetic acid), DTPA and DOTA. EDTA is preferred. To achieve the ironchelating effect, desferrioxamine and other siderophores may also be used, e.g. in conjunction with aminopolycarboxylic acid chelating agents such as EDTA.

The chelating agent may conveniently be used at a concentration of 1 to 20% eg. 2 to 10% (w/w).

Additionally, surface penetration assisting agents and especially dialkylsuLphoxides such as dimethylsulphoxide (DMSO) may have a beneficial effect in enhancing the photochemotherapeutic effect. This is described in detail in our co-pending application No. PCT/GB94/01951, a copy of the specification of which is appended hereto.

The surface-penetration assisting agent may be any of the skin-penetration assisting agents described in the pharmaceutical literature e.g. HPE-101 (available from Hisamitau), DMSO and other dialkylsulphoxides, in particular n-decylmethyl-sulphoxide (NDMS), dimethylsulphacetamide, dimethylformamide (DMFA), dimethylacetamide, glycols, various pyrrolidone derivatives (Woodford et al., J. Toxicol. Cut. & Ocular Toxicology, 1986, 5: 167-177), and Azone® (Stoughton et al., Drug Dpv. Ind. Pharm. 1983, 9: 725-744), or mixtures thereof.

DMSO however has a number of beneficial effects and is strongly preferred. Thus, in addition to the surface-penetration assisting effect (DMSO is particularly effective in enhancing the depth of penetration of the active agent into the tissue), DMSO has anti-histamine and anti-inflammatory activities. In addition, DMSO has been found to increase the activity of the enzymes ALA-synthase and ALA-dehydrogenase (the enzymes which, respectively, form and condense ALA to porphobilinogen) thereby enhancing the formation of the active form, Pp.

The surface penetration agent may conveniently be provided in a concentration range of 2 to 50% (w/w), eg about 10% (w/w).

According to the condition being treated, and the nature of the composition, the compounds for use in the invention may be co-administered with such other optional agents, for example in a single composition or they may be administered sequentially or separately. Indeed, in many cases a particularly beneficial photochemotherapeutic effect may be obtained by pre-treatment with the surface-penetration assisting agent in a separate step, prior to administration of the compounds for use in the invention. Furthermore, in some situations a pre-treatment with the surface-penetration assisting agent, followed by administration of the photochemotherapeutic agent in conjunction with the surface-penetration assisting agent may be beneficial. When a surface-penetration assisting agent is used in pre-treatment this may be used at high concentrations, e.g. up to 100% (w/w). If such a pre-treatment step is employed, the photochemotherapeutic agent may subsequently be administered up to several hours following pre-treatment eg. at an interval of 5-60 minutes following pre-treatment.

Viewed from a further aspect, the invention thus provides a product comprising a compound as described hereinbefore or a pharmaceutically acceptable salt thereof, together with at least one surface-penetration assisting agent, and optionally one or more chelating agents as a combined preparation for simultaneous, separate or sequential use in treating disorders or abnormalities of external or internal surfaces of the body which are responsive to photochemotherapy.

Alternatively viewed, this aspect of the invention also provides a kit for use in photochemotherapy of disorders or abnormalities of external or internal surfaces of the body comprising:

-   a) a first container containing a compound as described hereinbefore     or a pharmaceutically acceptable salt thereof, -   b) a second container containing a carrier and optionally in the     same or a third container at least one surface penetration assisting     agent; and optionally -   c) one or more chelating agents contained either within said first     container or in an additional container.

For example, a kit could comprise a first container containing 100 mg HAL hydrochloride and a second container containing 50 ml PBS (e.g. 4.3 mM KH₂PO₄, 4.3 mM Na₂HPO₄, 120 mM NaCl, pH 6.0).

Where the surface penetration agent is applied in a separate pre-treatment step, it may be applied in higher concentration, for example up to 10% (w/w).

In another aspect of the invention, the composition of the invention is used to diagnose or treat bladder cancer. In a further preferred embodiment, the composition is applied as a solution, for example a sterile isotonic solution, for example hexyl aminolevulinate in PBS. The sterile isotonic solution can be prepared, for example, by combining the contents of two containers, the contents of the first container being hexyl aminolevulinate, for example, and the contents of the second container being, for example, an isotonic solution such as PBS. Preferably the interiors of the containers and the containers' contents are sterile. In a yet further preferred embodiment, the solution is applied to the tissue to be treated or diagnosed by means of an endoscope.

As used herein, the term isotonic means having an osmotic pressure equal to that within a cell, for example, the cells of the tissue that is being diagnosed or treated, for example bladder cells.

Use of such a composition to detect and treat urological lesions such as bladder cancer has several advantages. For example, a hexyl aminolevulinate composition requires as little as 1 hour instillation time. Hexyl aminolevulinate also produces strong fluorescence, good tissue penetration, high selectivity for lesionous tissue, and has a relatively low effective drug concentration. Further, because a hexyl aminolevulinate composition can be made and used at or near physiological pH, it does not irritate the tissue being treated.

It will be appreciated that the method of therapy using compounds as described hereinbefore inevitably involves the fluorescence of the disorder or abnormality to be treated. Whilst the intensity of this fluorescence may be used to eliminate abnormal cells, the localization of the fluorescence may be used to visualize the size, extent and situation of the abnormality or disorder. This is made possible through the surprising ability of ALA esters to preferentially localize to non-normal tissue.

The abnormality or disorder thus identified or confirmed at the site of investigation may then be treated through alternative therapeutic techniques e.g. surgical or chemical treatment, or by the method of therapy of the invention by continued build up of fluorescence or through further application of compounds as described hereinbefore at the appropriate site. It will be appreciated that diagnostic techniques may require lower levels of fluorescence for visualization than used in therapeutic treatments. Thus, generally, concentration ranges of 1 to 50% e.g. 1-5% (w/w) are suitable. Sites, methods and modes of administration have been considered before with regard to the therapeutic uses and are applicable also to diagnostic uses described here. The compounds for use in the invention may also be used for in vitro diagnostic techniques, for example for examination of the cells contained in body fluids. The higher fluorescence associated with non-normal tissue may conveniently be indicative of an abnormality or disorder. This method is highly sensitive and may be used for early detection of abnormalities or disorders, for example bladder or lung carcinoma by examination of the epithelial cells in urine or sputum samples, respectively. Other useful body fluids which may be used for diagnosis in addition to urine and sputum include blood, semen, tears, spinal fluid etc. Tissue samples or preparations may also be evaluated, for example biopsy tissue or bone marrow samples. The present invention thus extends to the use of compounds as described hereinbefore, or salts thereof for diagnosis according to the aforementioned methods for photochemotherapy, and products and kits for performing said diagnosis.

A further aspect of the invention relates to a method of in vitro diagnosis, of abnormalities or disorders by assaying a sample of body fluid or tissue of a patient, said method comprising at least the following steps:

-   -   i) admixing said body fluid or tissue with a compound as         described hereinbefore,     -   ii) exposing said mixture to light,     -   iii) ascertaining the level of fluorescence, and     -   iv) comparing the level of fluorescence to control levels.

The invention will now be described in more detail in the following non-limiting Examples, with reference to the drawings in which:

FIG. 1 shows fluorescence intensity (relative units vs wavelength (nm)) of PpIX in the normal skin of mice after topical administration of

(A) free ALA

(B) ALA methylester

(C) ALA ethylester

(D) ALA propylester

after 0.5, 1, 1.5, 2.5, 3, 3.5 and 14 hours following administration;

FIG. 2 shows the distribution of PpIX as measured by fluorescence intensity (relative units vs wavelength (nm)) in Brain, dermis, Ear, Liver and muscle 14 hours after topical administration to the normal skin of mice:

(A) free ALA

(B) ALA methylester

(C) ALA ethylester

(D) ALA propylester;

FIG. 3 shows PpIX fluorescence (fluorescence intensity, relative units vs wavelength (nm)) in the skin of mice 15 minutes, 1 hour, 4 hours and 10 hours after intraperitoneal injection of ALA methylester (150 mg/kg);

FIG. 4 shows PpIX fluorescence (fluorescence intensity relative units vs wavelength (nm)) (A) 1.5 hours and (B) 4 hours after topical administration of ALA methylester to basal cell carcinoma (BCC) lesions on the skin of human patients (-tumour; - - - normal skin);

FIG. 5 shows PpIX fluorescence (fluorescence intensity relative units vs wavelength (nm)) (A) 1.5 hours and (B) 4 hours after topical administration of ALA ethylester to basal cell carcinoma (BCC) lesions on the skin of human patients (-tumour; - - - normal skin);

FIG. 6 shows PpIX fluorescence (fluorescence intensity relative units vs wavelength (nm)) (A) 1.5 hours and (B) 4 hours after topical administration of ALA propylester to basal cell carcinoma (BCC) lesions on the skin of human patients (-tumour; - - - normal skin);

FIG. 7 shows PpIX fluorescence (fluorescence intensity relative units vs wavelength (nm)) (A) 1.5 hours and (B) 4 hours after topical administration of ALA to basal cell carinoma (BCC) lesions on the skin of human patients (-tumour; - - - normal skin);

FIG. 8 shows measurement of PpIX production following topical application of ALA methylester in human BCC and surrounding normal skin by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 9 shows measurement of PpIX production following topical application of ALA in human BCC and surrounding normal skin by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 10 shows PpIX fluorescence (fluorescence intensity relative units vs wavelength (nm)) 24 hours following topical administration of ALA methylester to BCC lesion and to normal skin of human patients.

FIG. 11 shows PpIX fluorescence (fluorescence intensity relative units vs wavelength (nm)) 24 hours following topical administration of ALA to BCC lesion and to normal skin of human patients.

FIG. 12 shows measurement of PpIX production 4.5 hours following topical application of ALA methylester in human BCC by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 13 shows measurement of PpIX production 4.5 hours following topical application of ALA methylester in human normal skin by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 14 shows measurement of PpIX production 24 hours following topical application of ALA methylester in human BCC by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 15 shows measurement of PpIX production 24 hours following topical application of ALA methylester in human normal skin by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 16 shows measurement of PpIX production 24 hours following topical application of free ALA in human BCC by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 17 shows measurement of PpIX production 24 hours following topical application of free ALA in human normal skin by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 18 shows measurement of PpIX production 4.5 hours following topical application of free ALA and 20% DMSO in human BCC by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 19 shows measurement of PpIX production 4.5 hours following topical application of free ALA and 20% DMSO in human normal skin by CDD microscopy of biopsies (A) graphical representation showing fluorescence intensity vs depth (μm) and (B) micrograph;

FIG. 20 shows a time course (fluorescence intensity relative units vs time (hours)) of ALA methylester induced (PpIX) fluorescence in the mouse skin after topical application of ALA methylester alone (-●-), ALA methylester plus DMSO (-▴-), ALA methylester plus desferrioxamine (DF) (-▪-) or ALA methylester plus DF and DMSO (-▾-). Each point is the mean of measurements from at least three mice;

FIG. 21 shows fluorescence photographs of the mouse skin taken 1 h after topical application of free ALA alone (A), ALA methylester (B), ALA ethylester (C) and ALA propylester (D), showing fluorescence in the epidermis (Ep), epithelial hair follicles and sebaceous gland (arrows), but not in the dermis (De). Original magnification ×250.

FIG. 22 is a graph showing relative tumour volume against time (days) following treatment of WiDr human colonic carcinoma transplanted subcutaneously into nude mice with ALA or ALA methylester plus DF; (-▴-) control; (-▾-) DF alone; (-▪-) ALA+DF+DMSO; (-●-) ALA methylester+DF+DMSO.

FIG. 23 shows PpIX fluorescence ratios between BCC lesions and surrounding normal skin after topical application of ALA or its esters.

FIG. 24 shows images of cervical intraepithelial neoplasia after application of acetic acid (3%) (white light) and after application of hexaminolevulinic acid (0.5%).

FIG. 25 shows cervical intraepithelial neoplasia and surrounding tissue after thirty minutes application of hexaminolevulinate.

FIG. 26 shows cervical intraepithelial neoplasia and surrounding tissue after seventy-five minutes application of hexaminolevulinate.

FIG. 27 shows cervical intraepithelial neoplasia and surrounding tissue after three hours application of hexaminolevulinate.

FIG. 28 shows fluorescence from HAL-induced PpIX in bladder carcinoma cells collected from a patient's urine sample.

FIG. 29 shows the size (i.e. light scattering) of fluorescent cells that (y-axis) and the intensity of their fluorescence (x-axis) after incubation with HAL

FIG. 30 shows the relative level of induced fluorescence as a function of concentration of 5-aminolevulinic acid and several alkyl aminolevulinates.

FIG. 31 shows tissue samples with flat cancer lesions of the bladder (carcinoma in situ) visualized under white light and under blue light after treatment with a HAL composition.

EXAMPLE 1 Preparation of methyl 5-aminolevulinate hydrochloride

To a 500 ml glass reactor containing 200 ml methanol, was added 1 gram 5-amino-levulinic acid hydrochloride and 1 drop conc. HCl. The reaction mixture was then stirred overnight at 60° C. The progress of the esterification was followed by ¹H-NMR. Excess methanol was removed by distillation, and the product further dried under vacuum at 30-40° C., giving methyl 5-aminolevulinate hydrochloride. The structure was confirmed by ¹H-NMR in DMSO-d₆.

EXAMPLE 2 Preparation of ethyl 5-aminolevulinate hydrochloride (ALA ethylester)

1 g 5-aminolevulinic acid hydrochloride was added to 200 ml dry ethanol containing 1-2 drops conc. hydrochloric acid in a 250 ml glass reactor equipped with a stirrer, reflux condenser and a thermometer. The esterification was performed at ref lux overnight (70-80° C.). After the reaction had gone to completion, the ethanol was removed under vacuum. Finally, the product was dried under high vacuum at 30-40° C., giving 0.94 g Ethyl 5-aminolevulinate hydrochloride. Confirmation of the structure was done by ¹H-NMR in DMSO-d₆.

EXAMPLE 3 Preparation of n-propyl 5-aminolevulinate hydrochloride (Ala Propylester)

0.5 g 5-aminolevulinic acid hydrochloride was dissolved in 100 ml dry n-propanol containing 1-2 drops of conc. hydrochloride in a 250 ml glass reactor equipped with a stirrer, reflux condenser and a thermometer. The reaction mixture was stirred at 70-80° C. for approx. 20 hours. After all the 5-aminolevulinic acid was converted to its n-propylester (followed by ¹H-NMR), the excess propanol was removed, and the product dried under high vacuum (<1 mBar) at 40-50° C. The reaction gave 0.49 g propyl 5-aminolevulinate hydrochloride. The structure was confirmed by ¹H-NMR in DMSO-d₆.

EXAMPLE 4 Preparation of n-hexyl 5-aminolevulinate hydrochloride (Ala Hexylester)

2 grams of 5-aminolevulinic acid hydrochloride was dissolved in 25 grams of dry n-hexanol with 5-6 drops of conc. hydrochloride added in a 50 ml glass reactor equipped with a reflux condenser and a thermometer. The reaction mixture was held at 50-60° C. for approx. 3 days. The excess n-hexanol was removed under vacuum and the product finally dried under high vacuum, giving 2.4 grams of n-hexyl 5-aminolevulinate hydrochloride. The structure was confirmed by ¹H-NMR spectroscopy in DMSO-d₆.

EXAMPLE 5 Preparation of n-heptyl 5-aminolevulinic hydrochloride (Ala Heptylester)

0.5 g 5-aminolevulinic acid hydrochloride was added to 30 grams of n-heptanol containing 5 drops of conc. hydrochloride in a 100 ml glass reactor equipped with a stirrer, reflux condenser and a thermometer. After all the 5-aminolevulinic acid had dissolved, the reaction mixture was stirred at 70-80° C. for approx. 48 hours. After the 5-aminolevulinic acid was converted to its n-heptyl ester (followed by ¹H-NMR), the excess alcohol was removed, and the product dried under high vacuum (<1 mbar) at 70° C. The reaction gave 1.5 g n-heptyl 5-aminolevulinate hydrochloride. The structure was confirmed by ¹H-NMR in DMSO-d₆.

EXAMPLE 6 Preparation of n-octyl 5-aminolevulinic hydrochloride (Ala Octylester)

1 gram 5-aminolevulinic acid hydrochloride was added to 30 grams of dry n-octanol containing 5-6 drops of conc. hydrochloride in a 50 ml glass reactor equipped with a reflux condenser, stirrer and a thermometer. The reaction mixture was stirred at 65-70° C. for approx. 2 days. Excess n-octanol was removed under vacuum and the product finally dried under high vacuum, giving 1.5 grams of n-octyl 5-aminolevulinate hydrochloride. The structure was confirmed by ¹H-NMR spectroscopy in DMSO-d₆.

EXAMPLE 7 Formulation

20% creams were prepared by admixture of the active component, ALA, ALA methylester, ALA ethylester, or ALA propylester (prepared according to Examples 1 to 3 respectively), with “Urguentum Merck” cream base (available from Merck) consisting of silicon dioxide, paraffin liq., vaseline, album, cetostearol., polysorbat. 40, glycerol monostearate, Miglyol®812 (a mixture of plant fatty acids), polypropyleneglycol, and purified water.

Corresponding creams were also prepared, additionally containing 3-20% DMSO.

EXAMPLE 8 Determination of Protoporphyrin IX Production in the Skin of Mice by CCD Microscopy of Biopsies

A commercial oil-in-water cream containing (20% w/w) one of the chemicals (free ALA, ALA methylester, ALA ethylester and ALA propylester) (see Example 1) was topically applied to the normal skin of nu/nu nude mice for 0.5, 1, 3 and 6 hours, then biopsied and evaluated by means of microscopic fluorescence photometry incorporating a light-sensitive thermol-electrically cooled charge coupled device (CCD) camera. The results show that free ALA and its three ester derivatives are taken up by the skin tissue, the esterified ALA derivatives are being deesterified in the skin, and converted into protoporphyrin IX (PpIX) 0.5 hours after topical application. The fluorescence intensity of PpIX in the skin increased with the time of the application and the maximum amounts of the fluorescence were seen about 6 hours (the latest time point studied) after the application in all cases.

EXAMPLE 9 Measurements In Situ of Protoporphyrin IX Production in the Skin of Mice by an Optical-Fiber-Based System

The aim of this study was to investigate the build-up of esterified ALA ester-induced porphyrins fluorescence in the normal skin of nude mice in vivo after topical or systemic administration of ALA ester derivatives.

Materials and Methods

Chemicals. 5-aminolevulinic acid (ALA) methyl-, ethyl- and propyl-esters (H₂N—CH₂COOCH₂—CH₂COO—R; R can be CH₃, CH₂—CH₂—CH₃) were prepared by Norsk Hydro Research Center (Porsgrunn, Norway) as described in Examples 1 to 3. Free ALA hydrochloride and desferrioxamine mesylate (DF) were purchased from Sigma Chemical Company (St. Louis, Mo., USA). Dimethyl sulphoxide (DMSO) was obtained from Janssen Chimica (Geel, Belgium). Commercial oil-water creams (Unguentum Merck, Darmstadt, Germany) containing 20% one of the ALA ester derivatives (w/w), 20% free ALA, 20% ALA methylester plus 5% DF, 20% ALA methylester plus 20% DMSO, or 20% ALA methylester plus 5% DF and 20% DMSO were freshly prepared prior to use. All creams were made by the Pharmacy at the Norwegian Radium Hospital. For intraperitoneal injection, ALA and its methylester were freshly dissolved in saline. All other chemicals used were of the highest purity commercially available.

Animals. Female Balb/c nu/nu athymic nude mice were obtained from the Animal Laboratory at the Norwegian Radium Hospital and kept under specific-pathogen-free conditions. At the start of the experiments the mice were 6-7 weeks old weighing 18-24 g. Three mice were housed per cage with autoclaved covers in a dark room during the experiments.

Treatment procedure. One of the creams was painted on the normal skin at right flank region of each mouse, and covered by a semi-permeable dressing (3M, St Paul, Minn., USA) for various time intervals (from 0.25 to 24 h) before fluorescence measurements in situ or being biopsied for microscopic fluorescence imaging. About 0.2 g cream was applied to an approximate 2.25 cm² area of the skin. In the case of i.p. injection the mice were given ALA or its methylester at a dose of 150 mg/kg. At least three mice were used for each condition.

Fluorescence spectroscopic measurements in situ. A perkin Elmer LS-50 fluorescence spectrometer equipped with a red-sensitive photomultiplier (Hamamatsu R 928) was used. This instrument has a pulsed Xenon arc light source and phase sensitive detection, such that fluorescence can be readily measured. Part of the excitation beam (set at 408 nm for fluorescence measurements) was reflected into a 600 μm core multimodus optical quartz fiber (No. 3501 393, Dornier Medizintechnik, GmbH, Germering, Germany) by means of a mirror for application onto the subject through a hand held probe. Emission in the region of 550-750 nm was measured via emission fibres collecting information through the probe.

Fluorescence microscopy. After the creams were topically applied to the skin of mice for various times (as indicated above), the skin was biopsied and the frozen tissue sections were cut with a cryostat to a thickness of 8 μm. The fluorescence microscopy was carried out using an Axioplan microscope (Zeiss, Germany) with a 100 W mercury lamp. The fluorescence images were recorded by a light-sensitive thermoelectrically cooled charge coupled device (CCD) camera (resolution: 385×578 pixels with a dynamic range of 16 bits per pixel) (Astromed CCD 3200, Cambridge, UK) and hard copies on a video printer (Sony multiscan video printer UP-930). The filter combination used for detection of porphyrin fluorescence consisted of 390-440 nm excitation filter, a 460 nm beam splitter and a >600 nm emission filter.

Results

PpIX fluorescence was measured in situ by an optical-fiber based system in the normal skin of nude mice 0.5, 1, 1.5, 2.5, 3, 3.5 and 14 hours after topical application of free ALA or one of its ester derivatives as described above. As shown in FIG. 1, the PpIX fluorescence was already built-up 1 hour after topical application in the case of all derivatives, while the fluorescence was seen 1.5 hours after the application of free ALA. The maximum fluorescence intensity was found 14 hours after the application in all cases, but PpIX fluorescence induced from ALA esters in the skin was stronger than that from free ALA. Furthermore, as can be seen in FIG. 2, 14 hours after the application no fluorescence of ALA-esters-induced PpIX was detected in other areas of the skin and internal organs including ear, dermis, muscle, brain and liver. However, in the case of free ALA, a strong fluorescence was also seen in the ear as well as in the other areas of the skin. Thus, after topical application ALA-ester-induced PpIX was found locally in the skin, whereas free ALA-induced PpIX distributed not only locally, but also in other areas of the skin. We suggest that ALA is transported in the blood and that PpIX is subsequently formed in all organs containing the enzymes of the heme synthesis pathway and/or PpIX is formed in the skin and then transported to other tissues via blood circulation. The latter situation may lead to skin photosensitivity in areas where free ALA is not topically applied. In addition, after intraperitoneal injection of ALA methylester at a dose of 150 mg/kg, the PpIX fluorescence in the skin of mice was built-up 15 minutes after the injection and the peak value was found around 4 hours, and the fluorescence disappeared within 10 hours post the injection (FIG. 3). This kinetic pattern is similar to that of the fluorescence of free ALA-induced porphyrins in the skin following i.p. injection of the same dose, although the fluorescence decreased faster in the case of the ester than in the case of the free ALA.

EXAMPLE 10 Measurements of Protoporphyrin IX Production in Human Basal Cell Carcinoma (BCC) and Surrounding Normal Skin by Optical-Fiber Based System

The PpIX fluorescence in the BCC lesions and surrounding normal skin of human patients was measured in situ by optical-fiber based system after topical application of 20% free ALA and its derivatives for various time intervals.

FIGS. 4, 5, 6 and 7 show that, compared to free ALA, the ALA derivatives-induced PpIX was built up faster, produced more and localized more selectively in the BCC lesions (i.e. much less fluorescence in the surrounding normal skin), particularly for ALA methylester.

EXAMPLE 11 In Vivo Fluorescence Surface Measurements of PpIX Production in Human Bcc and Surrounding Normal Skin by CCD Microacgpv of Biopsies

In a 78 years old Caucasian male presenting multiple ulcero-nodular BCCs lesions were exposed to commercial oil-in-water creams containing either ALA alone (20 k w/w) or ALA methyl ester (20% w/w) (as described in Example 7) covered by a semi-permeable dressing for 24 hours. After removal of dressings and cream in vivo fluorescence was measured at the surface of tumor tissue and adjacent normal skin by means of a spectrofluorometer. Punch biopsies of the same areas were removed and samples were immediately immersed in liquid nitrogen. The tissue sections were cut with a cryostat microtome to a thickness of 8 μm. The localization pattern of the porphyrin fluorescence in the tissue sections was directly observed by means of fluorescence microscopy. The same frozen sections were subsequently stained with routine H&E staining for histological identification.

The same sections were subsequently stained with routine H&E staining for histological identification. Fluorescence microscopy was carried out with an Axioplan microscope (Zeiss, Germany). Fluorescence images and quantitative measurements were performed by a light-sensitive thermol-electrically cooled charge coupled device (CCD) camera (Astromed CCD 3200, Cambridge, UK) and an image processing unit (Astromed/Visilog, PC 486DX2 66 MHz VL). The main purpose for such quantitative measurements is to determine the exact penetration of ALA-induced porphyrins from tissue surface to the bottom layers of cancer lesions. The results are shown in FIGS. 8 and 9 in which the fluorescence intensity is expressed as a function of depth of cancer lesion.

As shown in FIGS. 8 and 9, an homogeneous distribution of PpIX fluorescence is seen from the top to the bottom of the whole BCC lesions after use of either free ALA or its methyl ester. This suggests that ALA methylester is at least as good as free ALA in terms of penetration and PpIX production in the BCC lesion. In addition, no PpIX fluorescence was seen in the surrounding normal skin after topical application of ALA methylester, indicating that ALA-methylester-induced PpIX highly selectively took place only in the BCC lesion.

In vivo fluorescence after 24 hours showed at least doubled fluorescence intensity for ALA methyl ester compared to ALA for the selected tumors and also an increase for corresponding normal tissues, however this only of about 50%. The ratio between tumor and normal tissue was about 1.2:1 for ALA and 2:1 for the ALA methyl ester. The results are shown in FIGS. 10 and 11.

At control one week after treatment all treatment fields presented a central necrotic area corresponding to the tumor. in the adjacent normal skin exposed to cream and light irradiation there was observed a marked erythema for the ALA while for the ALA methyl ester only moderate erythema was observed.

EXAMPLE 12 In Vivo Fluorescence Surface Measurements of PpIX Production in Human BCC and Surrounding Normal Skin by CCD Microscopy of Biopsies

The present data show the localization patterns and production of porphyrins (mainly protoporphyrin IX (PpIX)) after topical application of free ALA and one of its derivatives (methyl ester) for 4.5 and 24 hours in the nodular basal cell carcinomas (BCCS) and surrounding normal skin of patients. The tests were performed as described in Example 11.

Each of the following figures show both (A) fluorescence images of either the bottom layer of BCC lesions or of the surrounding normal skin. Curves indicating the fluorescence intensity as a function of depth of the BCC lesions or of the normal skin are also shown (B).

FIG. 12 shows a homogenous distribution of PpIX fluorescence generated by ALA methyl ester in the bottom layer of a BCC 4.5 hours after topical application. There is also some porphyrin fluorescence in surrounding normal skin (FIG. 13). The fluorescence intensity ratio between BCC and the normal skin is about 2. Moreover, the absolute amount of the fluorescence induced by ALA methyl ester is higher than that induced by free ALA and 20% DMSO after topical application for 4.5 hours, as shown below.

FIGS. 14 and 15 show a uniform distribution of porphyrin fluorescence induced by topical application of ALA methyl ester for 24 hours in the bottom layer of BCC and surrounding normal skin. The ratio of the fluorescence in BCC and that in normal skin is also about 2. Furthermore, the fluorescence intensity of ALA methyl ester-induced porphyrins in the BCC is almost twice as high as that in BCC after topical application of free ALA alone for 24 hours, as shown below.

FIGS. 16 and 17 show a homogenous distribution of free ALA-induced porphyrins in the bottom layer of BCC and surrounding normal skin 24 following topical application. However, the ratio of the fluorescence intensity between BCC and normal skin is about 1, which indicates a low selectivity of this treatment. Moreover the production of porphyrins in BCC is less than that in the case of ALA methyl ester.

FIGS. 18 and 19 show a homogenous distribution of ALA—induced porphyrins in the bottom layer of BCC and surrounding normal skin after topical application of free ALA and 20% DMSO for 4.5 hours. However, the ratio of the fluorescence intensity between BCC and normal skin is only slightly larger than 1, which demonstrates that the DMSO probably reduces the tumor selectivity of the porphyrins produced. Moreover, also in this case less porphyrins are produced in BCC than in the case of the application of ALA methyl ester.

EXAMPLE 13 Investigation of the Effects of the Chelating Agent Desferrioxamine (DF) and/or DMSO and Fluorescence of Skin

I. The effect of DF and/or DMSO on the build up of fluorescence in the normal skin of mice in situ was ascertained various times after topical administration of ALA-methylester. Methods were performed as described in Example 9.

Results

Topical application of the cream alone containing only DMSO did not show any fluorescence in the normal mouse skin, but there was some fluorescence of PpIX after DF alone was applied.

DF or DF plus DMSO (a well-known skin penetration enhancer) significantly enhanced the production of ALA methylester-induced PpIX.

II. Fluorescence imaging of the skin treated with three derivatives (performed as described in Example 9) showed fluorescence of the ester derivative-induced porphyrins in the epidermis, epithelial hair follicles and sebaceous glands 1 h after topical application (FIG. 21). The fluorescence intensity of the porphyrins increased with the time after the application.

SUMMARY

A large number of patients with basal cell carcinomas (BCCS) has topically been treated with ALA-based PDT in our hospital during the past five years and more than 90% of superficial BCCs have shown a complete regression. However, nodular BCCs had a low complete response rate due to a poor ALA retention and, consequently, a low ALA-induced porphyrin production in the deep layers of the lesions. In order to improve the technique, we used ALA ester derivatives instead of free ALA. The present data obtained presented in this Example and in Example 9 by means of both fluorescence spectroscopic measurements in situ and fluorescence microscopy of tissue biopsies, indicate that all three ester derivatives studied were taken up, de-esterified and finally converted into porphyrins in the epidermis, epithelial hair follicles and sebaceous glands of the nude mice with a higher porphyrin production than that of free ALA. This is in agreement with the preceding Examples concerning a study of human nodular basal cell carcinoma that demonstrate that the fluorescence of the ALA ester-induced porphyrins was built up faster with a higher intensity and a more homogenous distribution than those of free ALA-induced porphyrins in the lesions.

The present study also shows that DF has a significant effect in enhancing the production of ALA methylester-derived PpIX in the normal skin of the mice after topical application.

Interestingly, a strong fluorescence of free ALA-induced porphyrins was found in regions of the skin outside the area where the cream was topically applied (FIG. 2). This indicates that after topical application free ALA is transported in the blood and porphyrins are subsequently formed in all organs containing the enzymes of the heme synthesis pathway or porphyrins are initially formed in the skin or/and liver, then transported to other tissues via blood circulation. This may lead to skin photosensitivity in areas where free ALA is even not topically applied. However, none of the ester derivatives studied induced porphyrin fluorescence in other parts of the skin.

EXAMPLE 14

Effects of ALA methylester or ALA, DF and DMSO PDT on tumor growth in WiDr human colonic carcinoma-transplanted nude mice Nude mice were transplanted with WiDr human colonic carcinoma cells by subcutaneous injection into the right flank region. The following creams, formulated as described in the preceding Examples, were applied topically to the site of the tumor: 10% DF alone; 20% ALA+10% DF+20% DMSO; or 20% ALA methylester+10% DF+20% DMSO, followed, 14 hours later by laser light irradiation (632 nm, 150 mW/cm² for 15 minutes) A separate group of animals bearing the same tumor model, but receiving no topical application of the cream, served as a control. The responses of the treated tumors were evaluated as tumor regression/regrowth time. When the tumors reached a volume 5 times that of the volume on the day of light irradiation, the mice were killed. The results are shown in FIG. 22. (Bars: standard error of mean (SEM) based on 3-5 individual animals in each group). The results show that it took 34 days for tumors treated with ALA methylester+DF+DMSO to reach a volume five times that of the volume on the day just before light irradiation, whereas in the case of free ALA+DF+DMSO it took 24 days for the treated tumors to grow to 5 times size. Thus, ALA methylester is more effective than ALA in slowing tumor regrowth.

EXAMPLE 15 Selectivity of ALA Esters (Methyl, Hexyl, Heptyl and Octyl) for Non-Normal Tissue

The PpIX fluorescence ratios between BCC lesions and surrounding normal skin after topical application of ALA or its esters (20% for 4 hours), was examined using methods described in previous examples. The results are shown in FIG. 23 and indicate that all esters can more selectively induce PpIX in BCC lesions than free ALA, particularly in the case of ALA-methylester and ALA-hexylester.

EXAMPLE 16

Fluorescence detection of cervical intraepithelial lesion using hexyl aminolevulinate (HAL)

Materials and Methods

This study involved 32 non-pregnant women with histologically proven squamous intraepithelial lesions (CIN). Twenty-two patients had high grade lesions, 5 patients low-grade lesions and, as a control, 5 patients did not receive HAL.

5 to 20 ml of a cold-cream containing 0.5% (w/w) HAL hydrochloride was applied locally by means of a cervical cap. Random biopsies were performed at time points ranging from 5 min to 7 hours to assess the selective accumulation of HAL, as shown by fluorescence images. Image analysis on frozen tissue sections was carried out using a Zeiss Axiophot image analysis system.

Cold-cream - composition Ingredient Conc. (% v/v) Cetyl alcohol 21.0 Liquid paraffin 19.0 Monoleylsorbitane (SPAN 80) 0.5 Monoleylpolysorbitane (Tween 80) 4.5 Chlorhexidine digluconate 0.1 Distilled water ad 100% Results

A total of 112 biopsies were obtained from 32 patients. From these biopsies approximately 2000 fluorescence images were produced. Cervical lesions showed excellent fluorescence after topical application of HAL, as compared with standard image after the use of acetic acid 3% (FIG. 24). Fluorescence images from cervical biopsies of CIN lesions showed an excellent selectivity for precancerous lesions with a sharp demarcation towards lamina propria. The fluorescence was low after 5 minutes application, but application times of 30 minutes and longer showed a high and homogenous fluorescence throughout the lesion (FIGS. 25-27). Immediately after the biopsies were taken, the tissue was quickly frozen in liquid nitrogen and stored at −70° C. prior to use in order to stop any formation/degradation of cellular porphyrins. Tissue sections were prepared in the dark to avoid photobleaching. The frozen tissue blocks were mounted in Tissue Tek embedding compound (BDH) and a series of sections were prepared using a cryostat. Tissue sections were mounted on glass slides and images were recorded with a grey-scale camera. A band pass filter (BP395-440 nm) was used for excitation, while a second band-pass filter was used to record the specific Pp fluorescence. Autofluorescence (obtained from samples of patients that did not receive HAL) was measured as described above and subtracted. For longer application time, more than three hours, the selectivity was reduced. No local or systemic adverse reactions were noted after administration of HAL in any patients.

Discussion and Conclusion

Local application of HAL 0.5% to the cervix in patients with low- and high-grade intraepithelial neoplasia showed high and homogenous fluorescence in the lesions. Selectivity was excellent after 1-2 hour application of HAL 0.5% cream and the procedure was well tolerated. The correlation of these lesions with human papillomavirus infection is well established and it has been reported that virus-infected cells with capacity of synthesizing photoactive porphyrins are selectively eradicated by PDT (Malik et al., Br. J. Cancer (1987), 56: 589-595). This may further support the usefulness of PDT in these patients. The results are promising for further investigations to determine the efficacy of photodynamic therapy in this indication.

EXAMPLE 17 Photodynamic Therapy of Cervical Cancer Using HAL

A woman with a positive Pap-smear or for other reasons, is referred to colposcopy or HAL fluorescence imaging. For HAL fluorescence imaging, 10 ml 0.5% HAL gel is applied to the cervix by a cervical cap or gauze sponge for one hour, followed by blue light (375-440 nm) illumination for obtaining red fluorescence of dysplastic and malignant tissue (if present). Histology from biopsies of these lesions will confirm the presence of dysplasia/malignancy if present. Patients with dysplasia or malignancy receive HAL PDT if superficial lesions, or surgery if more invasive tumour. For PDT of superficial lesions, 10 ml HAL 0.5% gel is applied to the cervix for 12 hours, by self-administration or by a nurse. If endocervix is affected, the channel is cleaned for mucous and HAL gel is applied in this area by a cotton swab or the like before applying the cervical cap or gauze sponge. This is to ensure that the HAL gel reaches the crypts of the endocervical channel. After 12 hours the gel is removed and the cervix is illuminated with white or red light covering 630-635 nm, for example, 632 nm or 635 nm. Depending on the light used, the total light dose should be 50-100 J/cm² with a fluence of 100-200 mW/cm².

The effect of the treatment is evaluated after 6 weeks by a colposcopy or HAL imaging. If negative, the patient is followed up with Pap-smear colposcopy and HAL imaging according to the seriousness of disease. Residual lesions after HAL PDT may be re-treated with the same HAL dose regimen until clearance.

EXAMPLE 18 Detection of Bladder Cancer Cells in Urine

Urine of a patient with bladder cancer was centrifuged (1500 rpm for 5 min) and resuspended into cell growth medium containing 10% fetal calf serum and HAL hydrochloride (40 μg/ml or 0.15 mM) for 4 hours at 37° C. in the dark. The cells fluoresced under blue light (390-440 nm) after being incubated with HAL HCl (FIG. 28). Cytology showed that only cancer cells fluoresced; non-fluorescing cells were found to be normal (FIG. 28). FACS analysis of fluorescent cells is shown in FIG. 29 and demonstrates that it is medium-sized cells with high fluorescence (R3 frame in FIG. 29) that are the cancer cells. This was confirmed by cytology.

EXAMPLE 19 Comparison of HAL and ALA

It was shown that hexyl aminolevulinate induces maximum fluorescence in cells in vitro at a concentration of about 13 mM, and that this fluorescence is nearly three times the maximum fluorescence induced by aminolevulinic acid under the same conditions (FIG. 30). Human transitional cell carcinoma cells (T24) were used. ALA and ALA esters were dissolved in growth medium not containing serum. Fluorescence was observed using an excitation wavelength of 410 nm and detecting emission at 640 nm.

EXAMPLE 20 Detection of Lesions HAL Fluorescence Detection vs. White Light Cystoscopy

Photodynamic detection of bladder carcinoma in situ (CIS) (flat cancer lesions) after exposure to a hexyl aminolevulinate composition (8 mM HAL in PBS: 4.3 mM KH₂PO₄, 4.3 mM Na₂HPO₄, 120 mM NaCl, pH 6.0) for one hour was performed and compared to white light cystoscopy in patients with bladder cancer (FIG. 31).

About 50 ml of HAL solution was instilled into the bladder. The solution was allowed to remain in the bladder for one hour. After bladder evacuation, the bladder was inspected by using a cystoscope (Storz D-Light, Karl Storz, Tuttlingen, Germany) and mapped under white light followed by inspection and mapping of all fluorescing lesions using blue light (380-450 nm) (light of wavelength of about 405 nm could have been used as the PpIX absorption spectrum includes a maximum near 405 nm). After mapping of the lesions in white and blue light separately, biopsies and resected tissue were obtained of all lesions and suspicious areas. Finally, one biopsy from normal appearing urothelium (negative in white and blue light) was taken. Tissue material was prepared by the local pathologist and examined by both local and a central pathologist to verify the diagnosis.

In one study, 97% of CIS tumors were detected using HAL whereas only 59% of tumors were detected using cystoscopy. A total of 289 patients were enrolled, but 59 patients were training patients, nine were non-evaluable and three excluded for protocol violations, leaving 218 patients for analysis. The CIS lesion detection rate as verified by biopsies (including concomitant CIS), was found to be 97% with HAL and 58% with standard cystoscopy. The number of falsely detected lesions was low for both HAL (13%) and standard cystoscopy (10%).

In another study, an HAL composition detected 98% of tumor lesions in patients (regardless of tumor type), whereas use of white light identified only 73% of the lesions. The HAL solution composition and instillation and cystoscopy procedure is described above. The cystoscopy findings were verified by examination (by a pathologist) of 5 random biopsies taken from each patient. There were a total of 143 verified tumors in 45 patients including carcinoma in situ (CIS) and Ta or T1 lesions. HAL cystoscopy was performed in 43 of the patients with a detection rate of 96% (43/45). White light cystoscopy was performed in 33 of the patients with a detection rate of 73% (33/45).

In the study above, 13 patients had CIS lesions only. Among these, the HAL composition (as above) and cystoscopy (as above) identified 92% (12/13) of carcinoma in situ lesions, whereas white light detection identified only 23% (3/13). Cystoscopy results were verified by analysis of biopsies as above.

EXAMPLE 21 Treatment of Bladder Cancer using HAL

Patients with clinical symptoms of bladder cancer are referred to cystoscopy, for example as a result of a positive urine cytology. Cystoscopy is performed with either a flexible or rigid endoscope for the visual inspection of the bladder. HAL imaging is used for this purpose by one hour bladder instillation of an 8 mM buffered solution (as in Example 20), followed by evacuation and subsequent inspection with white and blue light (375-440 nm). Papillary, superficial lesions will be resected (TUR) in the operating room and checked by HAL imaging. To ensure removal of residuals and prevent tumour seeding, HAL PDT is performed immediately thereafter or within 6 hours. There is no need for a new HAL instillation. HAL PDT is performed by blue (375-440 nm), white or red (covering 630-635 nm) light illumination giving a total of 10-100 J/cm² with a fluence of 50-200 mW/cm² depending on the light source used.

Patients with multiple tumours, high grade and large tumours, CIS and frequent recurrences receive additional local treatment to treat residuals, delay recurrence and prevent progression. Also, patients who are resistant to chemotherapy and/or BCG, or who don't tolerate these treatment modalities or cystectomy, may receive HAL PDT. HAL PDT is performed either in the operating room or as outpatient treatment. HAL 8-16 mM solution (as in Example 20) is instilled in the bladder for 1-2 hours with 0-4 hours resting time before illumination as described above. For outpatient HAL PDT, instillation of a local anaesthetic should be used (separately or combined) to reduce discomfort during treatment. HAL PDT is repeated 2-3 times 6-12 weeks apart if needed to clear all tumours. To prevent regrowth of tumours HAL PDT is performed yearly in a similar manner.

The person of ordinary skill in the art will understand that the invention is not limited to the embodiments disclosed herein. 

1. A method for the diagnosis of disorders or abnormalities of an internal surface of the body, comprising: (i) administering to the sites of investigation or affected surfaces a composition comprising a compound of formula (I) R² ₂N—CH₂COCH₂—CH₂CO—OR¹  (I) wherein, R¹ is alkyl; and each R² is independently hydrogen or alkyl; wherein each alkyl of R¹ and R² is optionally substituted by hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, amino, aryl, oxo or fluoro groups and is optionally interrupted by oxygen atoms; or a pharmaceutically acceptable salt thereof; and (ii) exposing said sites or surfaces to light, wherein the internal surface of the body is the lining of the intestine.
 2. The method of claim 1, wherein the composition is in the form of a tablet or capsule suitable for oral administration.
 3. The method of claim 1, wherein the composition is in the form of a solution suitable for oral or rectal administration.
 4. The method of claim 3, wherein the composition further comprises an aqueous carrier.
 5. The method of claim 1, claim 2, claim 3, or claim 4, wherein, in the compound of formula (I), R¹ represents an unsubstituted alkyl group and each R² is hydrogen.
 6. The method of claim 5, wherein the compound of formula (I) is ALA-methyl ester, ALA-ethyl ester, ALA-propyl ester, or ALA-hexyl ester.
 7. The method of claim 6, wherein the method is used to determine whether colorectal cancer may be present.
 8. The method of claim 7, wherein the compound of formula (I) is ALA-hexyl ester.
 9. The method of claim 8, wherein the compound in the composition is the hydrochloride salt of ALA-hexyl ester.
 10. The method of claim 1, wherein the concentration of the compound in the composition is 10-50% (w/w).
 11. The method of claim 10, wherein the concentration of the compound is 15-30% (w/w).
 12. The method of claim 1, wherein a period of 0.5-48 hours is permitted to elapse between administering the composition and exposing the sites or surfaces to light.
 13. The method of claim 12, wherein a period of 1 to 10 hours is permitted to elapse between administering the composition and exposing the sites or surfaces to light.
 14. The method of claim 1, wherein the light has a wavelength of 350-640 nm.
 15. A method for the diagnosis of disorders or abnormalities of an internal surface of the body, comprising: (i) administering to the sites of investigation or affected surfaces a composition comprising (a) a compound of formula (I) R² ₂N—CH₂COCH₂—CH₂CO—OR¹  (I) wherein, R¹ is alkyl; and each R² is independently hydrogen or alkyl; wherein each alkyl of R¹ and R² is optionally substituted by hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, amino, aryl, oxo or fluoro groups and is optionally interrupted by oxygen atoms; or a pharmaceutically acceptable salt thereof, and (b) one or more fatty substances; and (ii) exposing said sites or surfaces to light, wherein the internal surface of the body is the lining of the intestine.
 16. The method of claim 15, wherein the composition is in the form of a tablet or capsule suitable for oral administration.
 17. The method of claim 15, wherein the composition is in the form of a solution suitable for oral or rectal administration.
 18. The method of claim 17, wherein the composition comprises an aqueous carrier.
 19. The method of claim 15, claim 16, claim 17, or claim 18, wherein, in the compound of formula (I), R¹ represents an unsubstituted alkyl group and each R² is hydrogen.
 20. The method of claim 19, wherein the compound of formula (I) is ALA-methyl ester, ALA-ethyl ester, ALA-propyl ester, or ALA-hexyl ester.
 21. The method of claim 20, wherein the method is used to determine whether colorectal cancer may be present.
 22. The method of claim 21, wherein the compound of formula (I) is ALA-hexyl ester.
 23. The method of claim 22, wherein the compound in the composition is the hydrochloride salt of ALA-hexyl ester.
 24. The method of claim 15, wherein the concentration of the compound in the composition is 10-50% (w/w).
 25. The method of claim 24, wherein the concentration of the compound is 15-30% (w/w).
 26. The method of claim 15, wherein a period of 0.5-48 hours is permitted to elapse between administering the composition and exposing the sites or surfaces to light.
 27. The method of claim 26, wherein a period of 1 to 10 hours is permitted to elapse between administering the composition and exposing the sites or surfaces to light.
 28. The method of claim 15, wherein the light has a wavelength of 350-640 nm.
 29. A pharmaceutical composition comprising (a) a compound of formula (I) R² ₂N—CH₂COCH₂—CH₂CO—OR¹  (I) wherein, R¹ is alkyl; and each R² is independently hydrogen or alkyl; wherein each alkyl of R¹ and R² is optionally substituted by hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, amino, aryl, oxo or fluoro groups and is optionally interrupted by oxygen atoms; or a pharmaceutically acceptable salt thereof, and (b) one or more fatty substances.
 30. The composition of claim 29, wherein the composition is in the form of a tablet or capsule suitable for oral administration.
 31. The composition of claim 29, wherein the composition is in the form of a solution suitable for oral or rectal administration.
 32. The composition of claim 31, wherein the composition comprises an aqueous carrier.
 33. The composition of claim 29, claim 30, claim 31, or claim 32, wherein, in the compound of formula (I), R¹ represents an unsubstituted alkyl group and each R² is hydrogen.
 34. The composition of claim 33 wherein the compound of formula (I) is ALA-methyl ester, ALA-ethyl ester, ALA-propyl ester, or ALA-hexyl ester.
 35. The composition of claim 34, wherein the compound of formula (I) is ALA-hexyl ester.
 36. The composition of claim 35, wherein the compound in the composition is the hydrochloride salt of ALA-hexyl ester.
 37. The composition of claim 29, wherein the concentration of the compound in the composition is 10-50% (w/w).
 38. The composition of claim 37, wherein the concentration of the compound is 15-30% (w/w). 